1. Field of the Invention
The present invention generally relates to a linear motion apparatus for performing a linear motion in an ultra high vacuum. More particularly, it relates to a linear motion apparatus under ultra high vacuum which performs a linear motion through contraction and expansion, does not need rear space to move, and achieves a stability because a rear projection is not necessary.
2. Description of the Conventional Art
In recent times, many modern manufacturing techniques such as a semiconductor fabrication require an ultra high vacuum. To maintain high precision and high purity, more and more fabrication processes need to be done in a vacuum chamber without exposure to air. For this, workpieces should be freely moved, transported, rotated, installed and detached in the vacuum condition. The trend of a large-sized vacuum equipment due to a mass-production has brought about a large-sized motion apparatus due to an increase of a moving distance. The same space has been required at the rear part of the equipment as the space corresponding to the travel distance of the linear motion apparatus. This need of additional space has given many restrictions to the system design.
A conventional linear motion apparatus will be described with reference to FIGS. 1A to 1F.
FIG. 1A shows a welded bellows seal. This apparatus gets the linear motion by dial turns of a handle, so that the handle holds longer length than the distance of an actual motion.
FIG. 1B shows a push-pull linear motion apparatus. The basics of this apparatus are similar to that of FIG. 1. But the moving method is different from that of FIG. 1. Specifically, a linear motion of FIG. 1B is achieved by a push-pull motion of a handle, and space is required toward the handle by the moving distance.
FIG. 1C shows a heavy duty linear motion apparatus; and FIG. 1D shows a heavy duty push-pull linear motion apparatus. Their operations are similar to those of FIGS. 1A-1B. But these apparatuses shown in FIGS. 1C-1D can support heavier weight, and also require the rear space by the moving distance.
FIG. 1E shows a rack-pinion linear motion apparatus. This apparatus converts a rotating motion of the rotary handle into a linear motion through a gear of a rail-shape, and requires a rail and space which correspond to a linear moving distance.
FIG. 1F shows a magnetically coupled sample transporting apparatus. This apparatus performs a linear motion by using a magnetic force to a cylindrical rod. While the moving distance is very long, this apparatus also needs space in the rear thereof by the moving distance. Since the apparatus is very long, it may get into a danger of collision.
In the aforementioned linear motion apparatuses, the rear space of the vacuum equipment is needed inevitably by the linear motion interval. Since a shaft is not bent or not folded in the linear motion mechanism of the conventional apparatus, the conventional apparatuses need double spaces of a corresponding portion in response to a forward moving distance. This results in over space longer than the moving distance in the rear thereof. Such space is not only unnecessary in installing the experimental equipments but also unstable because a long rod from the apparatus is protruded.